The present invention relates to the manufacture of blindaged glass to stop the trajectory of projectiles shot by firearms, and more particularly the invention relates to a light blindaged glass that protects the user against a fired projectile and against the glass fragments of the interior glass layer, and that said blindaged glass manufactured in accordance to the invention can be curved to be used in automobiles.
Due to the violence that has unraveled and extended in many countries and the indiscriminated use of firearms from politic extremists, fanatics and delinquents, it is also extending the use of automotive blindaged vehicles to protect both the passanger and the driver from these acts of vandalism.
It is logical that this type of vehicles must have heavy blindages in vital parts of the body creating a strong overweight that requires an engine of much greater power than the normal and, likewise, means of suspension, shock absorbance and brakes with a much greater degree of resistance. But to all that should be added the high weight of the blinkage crystals usually used in the front windshield, the back crystal and the small windows crystals which, due to the thickness that they must have and the high specific density of the glass, its total weight is high and excessively overcharges the weight of the blindaged vehicle with the correspondent incidence in the means of suspension, shock absorvence and brakes.
It should be considered that said blindage crystals are not only used in passenger vehicles but also in vehicles used to carry securities and even to be used in certain offices, establishments and dwellings, for which reason its excessive weight represents a limitative factor for said usage.
The conventional blindaged glass has scarcely distantiated from its original conception, that is the placement and lamination of a plurality of glass sheets with interposed films of polyvinyl butyral, being possible to laminate up to 12 sheets of glass with their correspondent interposed layers of polyvinyl butyral. To lessen the weight of these blindaged glasses and avoid the lacerating action of the fragments and glass splinters of the last sheet which confronts the user, it has been proposed, although with little success, to substitute part of the glass sheets with polycarbonate sheets that show good resistance to the perforation and temperature of the projectile. In such way said antibullet glasses are formed by three zones: the first one, by laminated glass; the second one, a vacuum chamber confines within a frame of elastomeric material, that allows the expansion of the projectile and the third one, formed by very thick layers of polycarbonate for the contention purposes. The main inconvenience of this method is the impossibility of curving said blindaged crystals altogether with the polycarbonate, in a symmetric and regular form with the empty space, to form a entirety that substitutes the conventional blindaged glass for automobiles, for which reason this product can only be obtained in a planar form.
The most recent technique proposes the placement of a polycarbonate sheet in the interior of a compound of laminated glasses with polyvinyl butyral.
This sheet of polycarbonate that normally has 6 mm. of thickness, allows to reduction of the number of glass sheets with which is obtained a reduction in the total weight of the product. However, the disadvantage of this blindaged compound is that such thick sheet of polycarbonate suffers with the changes of temperature, contractions and expansions so extended that can not be absorbed by the layers of polyurethane used as adherent, which causes delaminations (separation of sheets), loosing like that the compound resistance and the visibility that it should have.